Related Experiment Video

Updated: Jun 16, 2026

Silencing of BRCA2 to Identify Novel BRCA2-regulated Biological Functions in Cultured Human Cells
09:24

Silencing of BRCA2 to Identify Novel BRCA2-regulated Biological Functions in Cultured Human Cells

Published on: August 12, 2015

Inhibition of poly(ADP-ribose) polymerase down-regulates BRCA1 and RAD51 in a pathway mediated by E2F4 and p130

Denise Campisi Hegan1, Yuhong Lu, Gregory C Stachelek

  • 1Departments of Therapeutic Radiology, Yale University School of Medicine, New Haven, CT 06520, USA.

Proceedings of the National Academy of Sciences of the United States of America
|February 6, 2010
PubMed

Insights

Poly(ADP-ribose) polymerase (PARP) inhibitors harm hypoxic cancer cells by blocking DNA repair. Unexpectedly, PARP disruption also inhibits homology-dependent repair (HDR) by suppressing BRCA1 and RAD51 expression.

Area of Science:

  • Molecular Biology
  • Cancer Research
  • DNA Repair Mechanisms

Background:

  • Poly(ADP-ribose) polymerase (PARP) inhibitors are investigated for cancer therapy due to PARP's role in base excision repair (BER).
  • PARP inhibition is toxic to hypoxic cancer cells where homology-dependent repair (HDR) is typically reduced.

Purpose of the Study:

  • To investigate the effect of PARP inhibition on DNA repair pathways, specifically HDR.
  • To elucidate the mechanism by which PARP influences HDR and its implications for cancer therapy.

Main Methods:

  • Utilized chemical PARP inhibitors and siRNAs targeting PARP-1 to disrupt PARP function.
  • Assessed the expression of key HDR factors BRCA1 and RAD51.
  • Investigated the role of E2F4/p130 complexes in regulating BRCA1 and RAD51 promoter activity.
  • Employed a GFP-based assay to directly measure HDR efficiency.
  • Evaluated cytotoxicity and radiosensitivity in response to PARP inhibition and p130 modulation.

Main Results:

  • PARP inhibition, via chemical inhibitors or siRNA, unexpectedly suppressed HDR by down-regulating BRCA1 and RAD51 expression.
  • PARP inhibition led to increased occupancy of BRCA1 and RAD51 promoters by repressive E2F4/p130 complexes.
  • Disruption of p130, through HPV E7 expression or siRNA, reversed the cytotoxicity and radiosensitivity associated with PARP inhibition.
  • Direct measurements confirmed reduced HDR in cells treated with PARP inhibitors.

Conclusions:

  • PARP plays a regulatory role in DNA repair, influencing HDR by modulating BRCA1 and RAD51 expression through the E2F4/p130 pathway.
  • The down-regulation of BRCA1 and RAD51 is central to the effects of PARP inhibition on DNA repair and cellular response.
  • Findings suggest novel strategies for combination cancer therapies targeting PARP and HDR pathways.

More Related Videos

Detection of DNA Breaks in Dividing Human Cells by Neutral Comet Assay05:55

Detection of DNA Breaks in Dividing Human Cells by Neutral Comet Assay

Published on: August 23, 2024

Assessment of Global DNA Double-Strand End Resection using BrdU-DNA Labeling coupled with Cell Cycle Discrimination Imaging06:44

Assessment of Global DNA Double-Strand End Resection using BrdU-DNA Labeling coupled with Cell Cycle Discrimination Imaging

Published on: April 28, 2021

Related Concept Videos

Negative Regulator Molecules01:23

Negative Regulator Molecules

Positive regulators allow a cell to advance through cell cycle checkpoints. Negative regulators have an equally important role as they terminate a cell’s progression through the cell cycle—or pause it—until the cell meets specific criteria.
Restarting Stalled Replication Forks02:37

Restarting Stalled Replication Forks

DNA replication is initiated at sites containing predefined DNA sequences known as origins of replication. DNA is unwound at these sites by the minichromosome maintenance (MCM) helicase and other factors such as Cdc45 and the associated GINS complex.The unwound single strands are protected by replication protein A (RPA) until DNA polymerase starts synthesizing DNA at the 5’ end of the strand in the same direction as the replication fork. To prevent the replication fork from falling apart, a...
Abnormal Proliferation02:23

Abnormal Proliferation

Under normal conditions, most adult cells remain in a non-proliferative state unless stimulated by internal or external factors to replace lost cells. Abnormal cell proliferation is a condition in which the cell's growth exceeds and is uncoordinated with normal cells. In such situations, cell division persists in the same excessive manner even after cessation of the stimuli, leading to persistent tumors. The tumor arises from the damaged cells that replicate to pass the damage to the daughter...
DNA Damage can Stall the Cell Cycle02:36

DNA Damage can Stall the Cell Cycle

In response to DNA damage, cells can pause the cell cycle to assess and repair the breaks. However, the cell must check the DNA at certain critical stages during the cell cycle. If the cell cycle pauses before DNA replication, the cells will contain twice the amount of DNA. On the other hand, if cells arrest after DNA replication but before mitosis, they will contain four times the normal amount of DNA. With a host of specialized proteins at their disposal,cells must use the right protein at...
DNA Damage Can Stall the Cell Cycle02:36

DNA Damage Can Stall the Cell Cycle

In response to DNA damage, cells can pause the cell cycle to assess and repair the breaks. However, the cell must check the DNA at certain critical stages during the cell cycle. If the cell cycle pauses before DNA replication, the cells will contain twice the amount of DNA. On the other hand, if cells arrest after DNA replication but before mitosis, they will contain four times the normal amount of DNA. With a host of specialized proteins at their disposal,cells must use the right protein at...
Inhibition of Cdk Activity02:34

Inhibition of Cdk Activity

The orderly progression of the cell cycle depends on the activation of Cdk protein by binding to its cyclin partner. However, the cell cycle must be restricted when undergoing abnormal changes. Most cancers correlate to the deregulated cell cycle, and since Cdks are a central component of the cell cycle, Cdk inhibitors are extensively studied to develop anticancer agents. For instance, cyclin D associates with several Cdks, such as Cdk 4/6, to form an active complex. The cyclin D-Cdk4/6 complex...